FIGS. 1 and 2 illustrate conventional approaches to creating an image file which contains files and folders selected from among files and folders stored on a volume for access by a computer, and doing so without permanently losing user data from the source volume. The process illustrated in FIG. 1 backs up the volume to an image file, deletes unwanted files and/or directories from the volume, takes an image of the reduced volume into a second image file, and then restores the volume from the first image file. The process illustrated in FIG. 2 backs up the volume to another disk (or set of disks), deletes unwanted files and/or directories from the backup disk, and then images the backup disk.
Other approaches (often referred to as “file-by-file” approaches) are also known for making a copy of selected files or folders from a volume. However, file-by-file approaches do not create an “image” as that term is used in this document. An image is created in a block-by-block manner, and reflects that by typically preserving low-level block allocation assignments. This may be evident, for instance, in the preservation of file fragmentation, and the preservation of optimizations that reduce disk head movement. Images may thus be created in a sector-by-sector, cluster-by-cluster, or other low-level allocation-unit-by-allocation-unit manner, as opposed to being created in a file-by-file manner. Images are found, for instance, in the *.v2i files created and used by commercially available imaging software tools from Symantec's PowerQuest Division, such as V2I PROTECTOR or V2I BUILDER software (marks of Symantec Corporation PowerQuest Division).
To perform the process shown in FIG. 1, one must have enough available space on some storage medium to make the image A. During at least part of the FIG. 1 process, one is hindered or prevented from allowing the source computer to function normally because files are missing from the source. One may also need to move large amounts of data to make the image A, and to restore the source. The process shown in FIG. 2 may be considered an improvement over that shown in FIG. 1, in that the source data is only copied once, to temp, instead of being copied twice (source to image A, then image A to source). However, under the process of FIG. 2 one must generally move a full copy of source to temp, and one must have enough available space in temp to hold the copy.
Similar considerations apply when it is desired to obtain an image of only selected items from multiple volumes, and also apply regardless of whether the desired item(s) includes files, folders (e.g., directories), or both.